Antilock-breaking (ABS) vs Stabilty Control (ESP) vs Traction Control Video

[mouser]

Nice video(s) showing how the various car safety features work to solve different problems (Antilock-breaking (ABS) vs Stabilty Control (ESP) vs Traction Control):

Fast forward to 4 minutes in to see the tests.

[Deozaan]

Wow. Pretty neat!

[Stoic Joker]

While all of these are good systems, it should be mentioned that in the interest of safety they shouldn't be depended on. Because as with all things mechanical, there is always the potential for them to malfunction. I've ripped into salesman on several occasions when they started telling people that all you have to do is clamp down on the breaks and let the ABS handle everything ... Which IMO is a great way to get somebody killed by teaching them bad habits.

When ABS kicks in you can feel the system pulsing. That pulsing is the system's way of telling you that you need to back off the brakes a bit to maintain traction (and steering control). So as a teaching aid they're brilliant...but as a policy they encourage bad driving habits that could easily get one killed. Because if they happen to malfunction when you really need them, it's best to have proper braking technique to fall back on.

Electronic Stability Control I haven't played with, but I would apply the same caution to its usage as well. If you watch the video carefully you will notice that in the first non-ESC run he was jerking the wheel much harder than is prudent on hard and dry asphalt...let alone on ice. Now I'm assuming it was mainly for dramatic effect to help demonstrate the capabilities of the system. But having spent a good deal of time in various vehicles at speed I can assure you that sudden jerky control input is an absolute no-no. Everything should be done smoothly, and in harmony with vehicle attitude ... Assuming of course your intent is to keep it on the wheels..

Traction Control? I love it on my wife's new Dodge Charger. Launching it hard in the rain is almost boringly easy. But I did disable it on my bike because I occasionally need/like/want it to slide a bit ... Just for the entertainment value.

[mouser]

When ABS kicks in you can feel the system pulsing. That pulsing is the system's way of telling you that you need to back off the brakes a bit to maintain traction

This is the only part of your post I would take issue with.

I am no expert, but the experts seem to be pretty consistent in saying that if you have ABS, and you feel it kick in during a hard/emergency breaking scenario, you should *NOT* ease up on the breaks or "tap" the breaks as you were taught in the non-abs days.

In such emergency breaking, apply consistent pressure and let the ABS do it's job.

Perhaps a better way to say what you were trying to get at is that ABS should only be kicking in during "emergency" breaking; if you are using your breaks in a way that is triggering ABS, and it's not an emergency -- then you are driving badly -- and you should take it as a signal that you need to change your everyday breaking habits.

[Stoic Joker]

Tap/pulse (for snow driving) no, then you're just fighting the system for a rhythm ... But if it's rattling like hell you're not going to lose any breaking by backing off it a touch, and it'll help with steering input.

I've heard experts go both ways on this. Generally speaking however only the beginner courses recommend keeping it pinned. Advanced driving courses...not so much. My own experience - having spent a good bit of time on the ragged edge - as well has shown that ABS is not infallible. They are great systems - and having ABS was a big selling point for my current ride - but they are not magical. And as we both know even with the best intended input computers can sometimes get it wrong.

[mouser]

Anyone have other good instructional driving videos (for beginners):

Here's a series that I just found that I like:
https://www.youtube....LkbV7FbA5BZAA/videos

[TaoPhoenix]

Tough call here.

Driving reflexes are a bit tricky, and if two types of vehicles "encourage" opposite styles of driving like this whole ABS discussion, that feels tricky. I don't know what to think. I'm only a mediocre driver, and in an emergency I don't think I'm fast enough to figure out which of two braking reflexes I should be using!

[IainB]

When ABS kicks in you can feel the system pulsing. That pulsing is the system's way of telling you that you need to back off the brakes a bit to maintain traction

This is the only part of your post I would take issue with...

-mouser (June 10, 2014, 07:28 AM)

That all looks like a gross misconception - potentially dangerous too.

ABS works simply by momentarily relieving hydraulic brake pressure to any wheel where the relevant sensors feed back to the control system that the wheel is about to stop rotating (i.e., lock up) when the car is in motion. Thus, no matter how hard you slam on the brakes, the wheels will not (theoretically cannot) lock up, and hence the pulsing sensation.

From memory, the first "production" car to have ABS fitted was probably the very up-market and (then) revolutionary 1965 Jensen FF, which had a torque-split LSD (limited slip differential) four-wheel drive system (based on racing car tested systems), was fitted with four-wheel disc brakes and the Dunlop-Maxaret antilock braking system (which was based on aeronautical systems).

In terms of road safety, ABS was arguably one of the most important modern developments for potentially significantly reducing the incidence of accidents. It seems a crime that it is still not fitted as a compulsory standard on all modern road-going vehicles, large and small.
LSD 4WD systems would not be far behind in importance.

[SeraphimLabs]

When ABS kicks in you can feel the system pulsing. That pulsing is the system's way of telling you that you need to back off the brakes a bit to maintain traction

This is the only part of your post I would take issue with.

I am no expert, but the experts seem to be pretty consistent in saying that if you have ABS, and you feel it kick in during a hard/emergency breaking scenario, you should *NOT* ease up on the breaks or "tap" the breaks as you were taught in the non-abs days.

In such emergency breaking, apply consistent pressure and let the ABS do it's job.

Perhaps a better way to say what you were trying to get at is that ABS should only be kicking in during "emergency" breaking; if you are using your breaks in a way that is triggering ABS, and it's not an emergency -- then you are driving badly -- and you should take it as a signal that you need to change your everyday breaking habits.

-mouser (June 10, 2014, 07:28 AM)

You've pressed the brake, commanding the car to try and stop. But you've pressed so hard that the brakes locked up, triggering a skid. ABS senses that the wheel is sliding and reduces the brake pressure some to get it turning again in the interest of maintaining control. But then once the wheel is turning again the ABS clamps back down- making it skid again and repeating the cycle resulting in the pulsation and noise associated with the system. When that pulsation happens you are skidding your tires, resulting in a loss of traction and shortened tire life.

The correct response when you feel the ABS pulsing is to back off the brake slightly in order to preserve traction while still applying braking force. That way your wheels stay turning rather than breaking traction, but you are still applying very nearly as much braking force as road conditions will allow. In a panic braking situation the ABS intervenes to attempt to maintain traction, resulting in a far shorter stopping distance than what a skid would result in because of the increased control and keeping the wheels turning while braking.

I do like some of the traction control systems out there while driving. It is nice in slick conditions to avoid unwanted spins during acceleration. Haven't really put any of them to the test while braking though, nothing I drive is new enough to have that level of integration. But the classic Positraction differential, and the newer limited-slip centers really are worthwhile if free of mechanical defects. Its likely that the electric assists found in newer cars would have similar results in bad weather.

[mouser]

The correct response when you feel the ABS pulsing is to back off the brake slightly in order to preserve traction while still applying braking force.

Not to beat a dead horse, and again, i am a complete non-expert in driving, but I do think these instructions for what to do when ABS kicks in are in direct contradiction to widely agreed upon advice.

But again, this may be a result of not qualifying your advice.

I think it would be useful to separate the two scenarios of importance.

SCENARIO ONE - AN EMERGENCY STOP WHEN YOU NEED TO BRAKE AS QUICKLY AS POSSIBLE

*THIS* is the scenario that most experts are talking about.  In such a case, you, the above-average-but-not-super-human driver *CANNOT* outperform the ABS computer.  In such a case, you should depress firmly and ALLOW THE ABS TO PULSATE AND DO ITS JOB.  In such a case you do *NOT* want to be EASING UP on the brake -- that will prolong your stopping distance.  And you don't want to have to be trying to figure out in your brain how much pressure you should ease off while you are in a life or death panic and trying to steer around some obstacle.  Press hard and firm and let the ABS do its job.

SCENARIO TWO - NON-EMERGENCY BRAKING

In this scenario, your advice about easing up on the brake when ABS triggers is fine advice.  All you are saying is that the driver is triggering a skid or near-skid, and in a non-emergency scenario where you have plenty of braking distance, this is a sign that you are braking too hard.


More info:

• http://www.tc.gc.ca/...13082-abs2_e-215.htm
• http://www.nsc.org/n...Driving_with_ABS.pdf
• http://www.icbc.com/...uments/anti-lock.pdf

[CWuestefeld]

As others have said, one emphatically should not ease off until ABS stops pulsing.

The fact is that it's physically impossible to brake any better than ABS can, and anyone who tells you they can stop the car faster than if they just put it to the floor and let ABS handle it is lying.

The key here is that you've got just one brake pedal, so even if you've got the most sensitive reactions of any human, you can only give general directions to all wheels simultaneously. On the other hand, ABS can control each wheel independently. So if you're locking just one wheel, ABS can release pressure in that wheel's caliper while continuing to hold the other three. You simply cannot accomplish that with a single brake pedal.

There's one place where ABS logic fails, though. If you're in deep snow, having your wheels locked causes the snow to build up in front of you, and in some cases, the resistance of that piled snow exceeds what your braking force can achieve, so you would be better off just letting the wheels lock. But that's rare enough, and you're not probably qualified to make the determination, so best to let ABS do its thing.

The video in the OP showed that even with proper clutch technique, the traction control can do better than you.

So, as a driving enthusiast and go-kart racer, I think it's best to let the computer-aided safety measures do their thing and not try to take matters into my own hands.

Edit: spelling

[Stoic Joker]

In terms of road safety, ABS was arguably one of the most important modern developments for potentially significantly reducing the incidence of accidents. It seems a crime that it is still not fitted as a compulsory standard on all modern road-going vehicles, large and small.

-IainB (June 10, 2014, 09:48 AM)

Agreed, and also one of the biggest problems. Because if some one learns the stomp on it and pray method of ABS breaking, and then gets in a different vehicle that is not equipped with ABS ... Guess what is going to happen if they need to stop quickly. Or if they get into a panic stop situation and the ABS malfunctions. Neither scenario if far fetched, and in reality both are fairly common ... Because with all technology...Shit Happens. Which brings us back to my original point which was to stress the need for both learning and using proper breaking technique.

Not to mention that the brake system is designed to handle a certain peak operation pressure, and while it isn't necessarily possible to exceed that max system pressure in a single incident. Repeatedly subjecting the system to the excess pressure of someone just standing on the brakes until the ABS rattles like a maraca is quite likely to cause some component of the system to fail catastrophically. Because these ultra fancy new fangled systems are still based and dependent on the same $0.48 O-rings as the old systems which frequently blew out when someone nailed the petal with both feet hoping the then drum brakes could haul down a 6,000lb car from 80MPH before they got to the point of impact.

I'm not trying to argue that a skilled driver can stop faster than the ABS. I'm simply stating that a skilled driver will use the ABS to confirm the maximum friction point-of-lockup...and yes that includes panic stops. Having the ABS click a few time under hard breaking is fine, it lets you know that you are either close to the edge or crossing some very slick spots (like the painted lines). Clamping down on them until they rattle the whole car...is foolhardy at best.

[SeraphimLabs]

In a panic braking scenario you don't have time to think about how fast to pump the brakes or what pressure to use. You're going to clamp down on it by reflex and the ABS is going to do its job- that's why they created it.

But under normal driving conditions, if you hear the ABS buzzing you need to back off of it and conserve your traction.

And yes. Brake equipment can and will pop open at the worst possible times. I really hate working on a car's brakes because even though you just serviced them and changed a few things its always the component you didn't replace that bursts next time you make a panic stop.

ABS won't save you in the ruptured brake line scenario. It just makes you run out of fluid even faster, although I should hope that by now they've figured out how to make an ABS system that can cut off a leaking wheel to conserve fluid for wheels that are still working. Hydraulic fuses are a thing after all, aircraft use them for similar reasons to prevent loss of control accidents in the event of a fluid line rupture.

My car is one that ABS was optional on that model from the factory, and owners of that model quickly learned that the ABS system was a troublemaker- it tended to have the brakes get stuck on, ruining fuel economy and destroying the brake pads. So naturally the previous owner had disabled it. I see no reason to change that knowing that it is a faulty design of ABS and being used to hand-pumped brakes on older vehicles.

[mouser]

I'm thinking it might be smart to go to a parking lot somewhere and do some hard breaking to get a feel for stopping distance, and when+how ABS kicks in.
Would it be better/easier/less-stressful-for-me-and-car to do such a test in the rain or on dry pavement?

[SeraphimLabs]

You'll be more likely to feel it in the rain, due to the reduced traction- and the increased stopping distance of wet brakes.

In my experience most parking lots simply aren't large enough to let the car get up to its full highway speed before it is necessary to stop it again. On dry pavement when the car's traction and stopping distance are at their best you probably won't be able to get it to skid, which is necessary to make the ABS do its thing.  

On the other hand heavy rain with worn tires and you have a fairly good chance of triggering a skid through hydroplaning effects, allowing you to feel what the car will do when it loses traction. Wet brakes also are slower to take hold, so teaching yourself what the stopping distance is like on wet brakes will give you that much more safety margin in ideal conditions.

My personal preference for checking how the car reacts to variable traction is to go take a cruise on a backroad. Packed dirt and gravel roads are much more likely to result in skidding and sliding even in dry conditions than pavement is, and almost any vehicle can be sent sliding sideways on the turns.

[IainB]

If I couldn't get access to a local driver-training skid pan, I would usually do most of my skid control practice on a very wet or (preferably) ice-covered empty parking lot. In summer, I'd practice on loose-metalled roads.
I'd recommend it (practice) to anyone who wants to develop skill/ability in the control of a vehicle in road conditions which are difficult/dangerous with low friction/poor traction.
Failing that some driver-training schools provide mechanical skid inducing/simulation trolleys built around some of their vehicles on the skid pan.

Either way, learning/practicing on a skid-pan of some sort is much more preferable than leaving the learning till too late - i.e., in an actual on-road accident event.

By the way, in terms of the opening post, I would suggest that it is very much the case that the 3 systems mentioned - Antilock-breaking (ABS), Stabilty Control (ESP)and Traction Control are complementary rather than "versus" as is suggested in the post.
They will probably all be obligatory safety standards one day, with the final safety standard being the removal of the highest risk elements - i.e., the human driver and the Dunning–Kruger effect.

[CWuestefeld]

But under normal driving conditions, if you hear the ABS buzzing you need to back off of it and conserve your traction.

-SeraphimLabs (June 11, 2014, 08:00 AM)

Sorry. I don't want to be the jerk guy that just can't let something go on the Internet. But this is special because it directly affects the safety of each one of us, and I really don't want to let something like that lie.

Do not believe that you can achieve better results than the ABS, whether that's by backing off and trying to stay right on the limit, or any other trick.

The fact of the matter is that under any circumstance other than deep snow, the ABS will do better than you. It will also do better than Michael Schumacher, Ryan Hunter-Reay, or Sebastian Loeb. The limiting factor for a human is that there's only one brake pedal, so you cannot control each wheel individually. Thus, you cannot keep all four wheels at the limits of traction simultaneously. You're either going to have some at the limit and others locked and sliding, or you'll have none sliding, but not using all available traction. The ABS sensors watch each wheel individually, and modulate the pressure of each wheel individually, allowing each one to get closest to its greatest potential traction.

In Formula 1 racing, the cars have had ABS and traction control in the past. These technologies were all banned because they made the sport too boring: having the cars perform so perfectly took much of the interest out of the sport. Consider that F1 has said that ABS (and traction control) are, even for arguably the best twenty or so drivers in the world, an unfair advantage. No human, given the means of control we have, can do better than the ABS computer.

In 1997, the McLaren F1 team had a nifty idea. They added a 2nd brake pedal (where the clutch would have been in the old days), allowing the driver to send additional brake pressure to just one of the rear wheels. This innovation allowed the two McLaren drivers to lap the field. Once this innovation was discovered (by a photographer who stuck his camera down into a stopped car and quickly snapped a picture), it was quickly banned. If the addition of driver control of just one separate wheel was such a huge advantage, imagine what a difference separate control of each wheel makes.

Edit: typo

[mouser]

CWuestefeld, you have done a great job of explaining why ABS is going to do a better job than a human when one is in a dangerous situation -- and as you know from my posts in this thread, you and I are trying to make the same basic point about letting ABS do it's thing and not try to second guess it when you need to make a hard stop.

However -- I think it's fair to say that during normal driving, when you should have plenty of room to stop -- if your ABS is kicking in during non-emergency braking -- that's a sign that something needs correcting (either in your style of driving or in the mechanics of the car).  Either you are regularly braking too hard, or your brakes/tires need fixing.

I think that's where the other side in this debate is coming from.  With that in mind I would suggest that drivers who feel ABS come on, stick to the guidelines to continue to provide firm consistent pressure and let the ABS do it's job.  And then afterwords take the triggering of ABS as a signal that you were pushing your car too far over the safety line, and should adjust your driving or car to avoid such occurences in the future.

After all, we certainly don't want to leave people with the impression that their ABS braking system is so smart that they can just slam on the brakes whenever they want and ABS will save them from danger.

[IainB]

This is interesting! One never expected that one would be able to get unqualified driving tips/advice from DC Forums.
I just imagined a scenario where a Boeing 787Dreamliner was touching down on a nice dry runway and braking, and the captain saying to the co-pilot "Ease up on the brakes there Frank, I can feel the ABS kicking in a bit too much."

I wonder if that sort of scenario would ever be likely to occur?
(ABS was originally developed for aeronautical systems.)

[CWuestefeld]

I think that's where the other side in this debate is coming from.

-mouser (June 11, 2014, 10:06 AM)

Fair enough, mouser, and thanks for the injection of sanity. If I might sum up, then:

• In any particular incident, if you feel the ABS kicking in, and you really do need to stop quickly, you should maintain foot pressure to let the ABS do its job.
• If you find that you're using ABS in general, you should reconsider your driving. Are you going too fast for conditions? Are you over-driving your visibility so you've got less distance to react? Are you exceeding the capabilities of your equipment (check your tire wear and brakes)?

[mouser]

 

[SeraphimLabs]

This is interesting! One never expected that one would be able to get unqualified driving tips/advice from DC Forums.
I just imagined a scenario where a Boeing 787Dreamliner was touching down on a nice dry runway and braking, and the captain saying to the co-pilot "Ease up on the brakes there Frank, I can feel the ABS kicking in a bit too much."

I wonder if that sort of scenario would ever be likely to occur?
(ABS was originally developed for aeronautical systems.)

-IainB (June 11, 2014, 10:37 AM)

There's a very real chance that it actually does kick the ABS now that I think about it. When an aircraft first contacts the ground, there isn't a lot of weight on the wheels yet because the wings are still producing a lot of lift. The wheels will skid from low traction until the airspeed drops enough to transfer the weight, and a lot of runways have black streaks on them from repeated skids of incoming aircraft.

The difference is aircraft have far more frequent maintenance intervals, and have a much higher safety factor in the design because of how heavily regulated aircraft are. Having a brake line simply burst on an aircraft I should hope is an unheard-of event because of maintenance procedures dictating replacement of such components at set time periods.

On the other hand a car often isn't in the best of shape, and people tend to not realize stuff is about to break until it actually does. In the case of a brake line, your normal stop where you have plenty of distance and shouldn't rely on the automatic systems has now become an emergency stop because the loss of braking pressure means you don't have the stopping power you are used to. ABS won't help that situation at all, the automation frequently will throw a fault condition and shut down.

Having drivers in the habit of driving without relying on the automation means that when the automation fails unexpectedly, you still can remain in control of the vehicle and bring it to a safe stop assuming that the loss of stopping power doesn't make you run out of stopping distance or you are able to avoid the hazard and give yourself additional space.

Of course if the automation is working properly, it is hard to beat- and you almost certainly won't doing it by hand. But in the case of ABS, you should stay in the habit of not relying on it. Let it do its job during the emergencies it was designed to deal with, under more relaxed conditions the person driving should be making the decisions not the vehicle they are operating.

And yes. I think most of the debate over ABS was people agreeing that in an emergency stop scenario the ABS will beat the manual control every time, but under relaxed conditions it is better from a maintenance and driving habits standpoint to back off and retain manual control to reduce component wear.

[IainB]

Very droll.

[Stoic Joker]

After all, we certainly don't want to leave people with the impression that their ABS braking system is so smart that they can just slam on the brakes whenever they want and ABS will save them from danger.

-mouser (June 11, 2014, 10:06 AM)

And that is precisely the problem point that I was going after. Sales monkeys, and many of the tech showcase bits make it sound like magic, giving people the dangerously false impression that they can just wait for the last minute clamp down the binders and the computer will do the rest. The problem here is that the behavior accelerates wear on many components causing them to "drift" out of the spec's that the computers calculations are dependent on.

I'm almost 50 now. So I've had 35 years (actually over) of both performance driving and being a mechanic to test and observe how and when things fail. I tend to break very hard and very late in corners...because I can. I have the years of necessary experience to pull it off safely. The thing that scares my is the number of people in traffic I see that trigger the ABS just because they have once again blasted up to a corner or stop light in the rain way too fast thinking that the magical car stoppie thing will once again save their silly ass. Because someday it wont, if they keep doing that.

As SeraphimLabs mentioned the ABS is simply cycling to release the drivers excess breaking pressure. So depending on pad material, when done repeatedly this will either cause the pads to glaze so they lose grip, or groove the rotors (disks if you like) making it very difficult for the system to release breaking pressure. I've fried brakes both ways racing with different pads, and either malady can get quite interesting really fast. Another fun issue is that with the excess buildup of break dust it can frequently obscure the wheel speed sensors ability to "see" the wheel lock ... Guess what happens then.

-----------------------------------------------------------------------------------------------------------------------

@SeraphimLabs - Are you psychic or something? If your posts got any closer to what is going through my head I'd have to start getting paranoid!

[TaoPhoenix]

@SeraphimLabs - Are you psychic or something? If your posts got any closer to what is going through my head I'd have to start getting paranoid!

-Stoic Joker (June 11, 2014, 12:53 PM)

That's why I invited him to DC - because he has a lot to offer!